<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>Vue基础呀</title>
  </head>

  <body>
    <div id="app">
      <button @click="sub"> - </button>
      <span> {{num}} </span>
      <button @click="add"> + </button>

    </div>

    

    <!-- 开发环境版本，包含了有帮助的命令行警告 -->
    <script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>


    <script>
      new Vue({
        el:"#app",
        data:{
          num:2
        },
        methods: {
          add:function(){
            if(this.num <10){
              this.num++;
            }else{
              alert("到达最大值啦")
            }           
          },
          sub:function(){
            if(this.num >0){
              this.num--;
            }else{
              alert("到达最小值啦")
            }           
          }       
        }
      })

    </script>

    <!-- data是这个Vue实例中使用到的数据。用什么就写什么 -->
  </body>
</html>
